Autumn 2026 seasonal transitions and equinox dates

The transition to autumn in 2026 can be defined through two different systems: meteorological and astronomical.

Meteorological seasons align with calendar months and temperature cycles. According to the National Oceanic and Atmospheric Administration, meteorological autumn begins on September 1.

Astronomical seasons are determined by the Earth's position relative to the sun, specifically marked by equinoxes and solstices. In 2026, the autumnal equinox is expected to occur around September 22 or 23. During an equinox, the Earth's axis is not tilted toward or away from the sun, resulting in nearly equal amounts of daylight and darkness across the globe.

Following the equinox, the Northern Hemisphere will experience gradually decreasing daylight hours and increasing nighttime hours. The autumn season will conclude with the winter solstice on December 21.